Deep diving

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Wreck diver Trevor Jackson using a rebreather with open circuit bailout cylinders returning from a 600-foot (180 m) dive. Trevor Jackson returns from SS Kyogle.jpg
Wreck diver Trevor Jackson using a re­breather with open circuit bail­out cylinders returning from a 600-foot (180 m) dive.

Deep diving is underwater diving to a depth beyond the norm accepted by the associated community. In some cases this is a prescribed limit established by an authority, while in others it is associated with a level of certification or training, and it may vary depending on whether the diving is recreational, technical or commercial. Nitrogen narcosis becomes a hazard below 30 metres (98 ft) and hypoxic breathing gas is required below 60 metres (200 ft) to lessen the risk of oxygen toxicity. At much greater depths, breathing gases become supercritical fluids, making diving with conventional equipment effectively impossible regardless of the physiological effects on the human body. Air, for example, becomes a supercritical fluid below about 400 metres (1,300 ft).

Contents

For some recreational diving agencies, "Deep diving", or "Deep diver" may be a certification awarded to divers that have been trained to dive to a specified depth range, generally deeper than 30 metres (98 ft). However, the Professional Association of Diving Instructors (PADI) defines anything from 18 to 30 metres (59 to 98 ft) as a "deep dive" in the context of recreational diving (other diving organisations vary), and considers deep diving a form of technical diving. [1] [ page needed ] In technical diving, a depth below about 60 metres (200 ft) where hypoxic breathing gas becomes necessary to avoid oxygen toxicity may be considered a deep dive. In professional diving, a depth that requires special equipment, procedures, or advanced training may be considered a deep dive.

Deep diving can mean something else in the commercial diving field. For instance early experiments carried out by COMEX using heliox and trimix attained far greater depths than any recreational technical diving. One example being its "Janus 4" open-sea dive to 501 metres (1,640 ft) in 1977. [2] [3]

The open-sea diving depth record was achieved in 1988 by a team of COMEX and French Navy divers who performed pipeline connection exercises at a depth of 534 metres (1,750 ft) in the Mediterranean Sea as part of the "Hydra 8" programme employing heliox and hydrox. The latter avoids the high-pressure nervous syndrome (HPNS) caused by helium and eases breathing due to its lower density. [2] [4] [5] These divers needed to breathe special gas mixtures because they were exposed to very high ambient pressure (more than 54 times atmospheric pressure).

An atmospheric diving suit (ADS) allows very deep dives of up to 700 metres (2,300 ft). [6] These suits are capable of withstanding the pressure at great depth permitting the diver to remain at normal atmospheric pressure. This eliminates the problems associated with breathing pressurised gases. In 2006 Chief Navy Diver Daniel Jackson set a record of 610 metres (2,000 ft) in an ADS. [7] [8]

On 20 November 1992 COMEX's "Hydra 10" experiment simulated a dive in an onshore hyperbaric chamber with hydreliox. Théo Mavrostomos spent two hours at a simulated depth of 701 metres (2,300 ft). [2] [9] [10] [11] [12]

Depth ranges in underwater diving

Assumed is the surface of the waterbody to be at or near sea level and underlies atmospheric pressure.

Not included are the differing ranges of freediving  – without breathing during a dive.

Depth [nb 1] Comments
12 m (39 ft)Recreational diving limit for divers aged under 12 years old and EN 14153-1 / ISO 24801-1 level 1 (Supervised Diver) standard. [13]
18 m (60 ft)Recreational diving limit for Open Water Divers (e.g. PADI, NAUI).
20 m (66 ft)Recreational diving limit for EN 14153-2  ISO 24801-2 level 2 "Autonomous Diver" standard. [14]
21 m (69 ft) GUE Recreational Diver Level 1. [15]
30 m (98 ft)Recommended recreational diving limit for PADI Advanced Open Water divers [1] [ page needed ] and GUE Recreational Diver Level 2. [15] Average depth at which nitrogen narcosis symptoms begin to be noticeable in adults.
40 m (130 ft)Depth limit for divers specified by Recreational Scuba Training Council [1] [ page needed ] and GUE Recreational Diver Level 3. [15] Depth limit for a French level 2 diver accompanied by an instructor (level 4 diver), breathing air.[ citation needed ]
50 m (160 ft)Depth limit for divers breathing air specified by the British Sub-Aqua Club and Sub-Aqua Association. [16]
60 m (200 ft)Depth limit for a group of 2 to 3 French Level 3 recreational divers, breathing air. [17]
66 m (217 ft)Depth at which breathing compressed air exposes the diver to an oxygen partial pressure of 1.6 bar (23 psi). Greater depth is considered to expose the diver to an unacceptable risk of oxygen toxicity. [nb 2]
100 m (330 ft)One of the recommended technical diving limits. Maximum depth authorised for divers who have completed Trimix Diver certification with IANTD [18] or Advanced Trimix Diver certification with TDI. [19]
156 m (512 ft)Deepest scuba dive on compressed air (July 1999 in Puerto Galera, Philippines). [20]
200 m (660 ft)Limit for surface light penetration sufficient for plant growth in clear water, though some visibility may be possible farther down. [nb 3]
230 m (750 ft)First dive on a hydrox-rebreather (14 February 2023 in the Pearse Resurgence, New Zealand). [21]
290 m (950 ft)Deepest ocean dive on a rebreather (23 March 2014 in Gili Trawangan, Indonesia). [22]
312 m (1,024 ft)Deepest cave diving on a rebreather (6 January 2024 in Font Estramar, France).
316 m (1,037 ft)Deepest dive on a rebreather (10 October 2018 in Lake Garda, Italy). [23]
332 m (1,089 ft)Deepest scuba dive, deepest dive on trimix (18 September 2014 in Dahab, Egypt). [24] [25]
534 m (1,752 ft)COMEX Hydra 8 dives on hydreliox (February 1988 offshore Marseille, France). [2] [4] [10]

Particular problems associated with deep dives

Deep diving has more hazards and greater risk than basic open-water diving. [26] Nitrogen narcosis, the "narks" or "rapture of the deep", starts with feelings of euphoria and over-confidence but then leads to numbness and memory impairment similar to alcohol intoxication. [1] [ page needed ] Decompression sickness, or the "bends", can happen if a diver ascends too rapidly, when excess inert gas leaves solution in the blood and tissues and forms bubbles. These bubbles produce mechanical and biochemical effects that lead to the condition. The onset of symptoms depends on the severity of the tissue gas loading and may develop during ascent in severe cases, but is frequently delayed until after reaching the surface. [1] [ page needed ] Bone degeneration (dysbaric osteonecrosis) is caused by the bubbles forming inside the bones; most commonly the upper arm and the thighs. Deep diving involves a much greater danger of all of these, and presents the additional risk of oxygen toxicity, which may lead to convulsions underwater. Very deep diving using a helium-oxygen mixture (heliox) or a hydrogen-helium-oxygen mixture (hydreliox) carries the risk of high-pressure nervous syndrome and hydrogen narcosis. Coping with the physical and physiological stresses of deep diving requires good physical conditioning. [27]

Using open-circuit scuba equipment, consumption of breathing gas is proportional to ambient pressure  – so at 50 metres (164 ft), where the pressure is 6 bars (87 psi), a diver breathes six times as much as on the surface (1 bar, 14.5 psi). Heavy physical exertion makes the diver breathe even more gas, and gas becomes denser requiring increased effort to breathe with depth, leading to increased risk of hypercapnia  – an excess of carbon dioxide in the blood. The need to do decompression stops increases with depth. A diver at 6 metres (20 ft) may be able to dive for many hours without needing to do decompression stops. At depths greater than 40 metres (131 ft), a diver may have only a few minutes at the deepest part of the dive before decompression stops are needed. In the event of an emergency, the diver cannot make an immediate ascent to the surface without risking decompression sickness. All of these considerations result in the amount of breathing gas required for deep diving being much greater than for shallow open water diving. The diver needs a disciplined approach to planning and conducting dives to minimise these additional risks.

Many of these problems are avoided by the use of surface supplied breathing gas, closed diving bells, and saturation diving, at the cost of logistical complexity, reduced maneuverability of the diver, and greater expense.

Dealing with depth

Technical divers preparing for a mixed-gas decompression dive. Note the backplate and wing setup with side mounted stage tanks containing EAN50 (left side) and pure oxygen (right side). Decompression Dive-Preparation.JPG
Technical divers preparing for a mixed-gas decompression dive. Note the backplate and wing setup with side mounted stage tanks containing EAN50 (left side) and pure oxygen (right side).

Both equipment and procedures can be adapted to deal with the problems of greater depth. Usually the two are combined, as the procedures must be adapted to suit the equipment, and in some cases the equipment is needed to facilitate the procedures.

Equipment adaptations for deeper diving

The equipment used for deep diving depends on both the depth and the type of diving. Scuba is limited to equipment that can be carried by the diver or is easily deployed by the dive team, while surface-supplied diving equipment can be more extensive, and much of it stays above the water where it is operated by the diving support team.[ citation needed ]

Procedural adaptations for deeper diving

Procedural adaptations for deep diving can be classified as those procedures for operating specialized equipment, and those that apply directly to the problems caused by exposure to high ambient pressures.

Closed circuit rebreather (AP Diving "Inspiration"). Plongee-RecycleurInspiration 20040221-153656.jpg
Closed circuit re­breather (AP Diving "In­spi­ra­tion").

Ultra-deep diving

Mixed gas

Amongst technical divers, there are divers who participate in ultra-deep diving on scuba below 200 metres (656 ft). This practice requires high levels of training, experience, discipline, fitness and surface support. Only twenty-six people are known to have ever dived to at least 240 metres (790 ft) on self-contained breathing apparatus recreationally. [20] [28] [nb 4] [nb 5] The "Holy Grail" of deep scuba diving was the 300 metres (980 ft) mark, first achieved by John Bennett in 2001, and has only been achieved five times since.[ citation needed ] Due to the short bottom times and long decompression, scuba dives to these depths are generally only done for deep cave exploration or as record attempts.

The difficulties involved in ultra-deep diving are numerous. Although commercial and military divers[ citation needed ] often operate at those depths, or even deeper, they are surface supplied. All of the complexities of ultra-deep diving are magnified by the requirement of the diver to carry (or provide for) their own gas underwater. These lead to rapid descents and "bounce dives". This has led to extremely high mortality rates amongst those who practice ultra-deep diving.[ citation needed ] Notable ultra-deep diving fatalities include Sheck Exley, John Bennett, Dave Shaw and Guy Garman. Mark Ellyatt, Don Shirley and Pascal Bernabé were involved in serious incidents and were fortunate to survive their dives. Despite the extremely high mortality rate, the Guinness World Records continues to maintain a record for scuba diving [25] (although the record for deep diving with compressed air has not been updated since 1999, given the high accident rate). Amongst those who do survive significant health issues are reported. Mark Ellyatt is reported to have suffered permanent lung damage; Pascal Bernabé (who was injured on his dive when a light on his mask imploded [29] ) and Nuno Gomes reported short to medium term hearing loss. [30] [ unreliable source? ]

Serious issues that confront divers engaging in ultra-deep diving on self-contained breathing apparatus include:

Compression arthralgia
Deep aching pain in the knees, shoulders, fingers, back, hips, neck, and ribs caused by exposure to high ambient pressure at a relatively high rate of descent (i.e., in "bounce dives").
High-pressure nervous syndrome (HPNS)
HPNS, brought on by breathing helium under extreme pressure causes tremors, myoclonic jerking, somnolence, EEG changes, [31] visual disturbance, nausea, dizziness, and decreased mental performance. Symptoms of HPNS are exacerbated by rapid compression, a feature common to ultra-deep "bounce" dives.
Isobaric counterdiffusion (ICD)
ICD is the diffusion of one inert gas into body tissues while another inert gas is diffusing out. It is a complication that can occur during decompression, and that can result in the formation or growth of bubbles without changes in the environmental pressure.
Decompression algorithm
There are no reliable decompression algorithms tested for such depths on the assumption of an immediate surfacing. Almost all decompression methodology for such depths is based upon saturation, and calculates ascent times in days rather than hours. Accordingly, ultra-deep dives are almost always a partly experimental basis.[ citation needed ]

In addition, "ordinary" risks like size of gas reserves, hypothermia, dehydration and oxygen toxicity are compounded by extreme depth and exposure and long in-water decompression times. Some technical diving equipment is simply not designed for the greater pressures at these depths, and reports of key equipment (including submersible pressure gauges) imploding are not uncommon.[ citation needed ]

Verified scuba dives to at least 240 metres (790 ft)
NameLocationTADepthYear
Ahmed Gabr [24] [32] [33] Dahab, Egypt OW OC 332 m (1,090 ft)2014
Nuno Gomes [28] [34] [35] Dahab, Egypt OW OC 318 m (1,040 ft)2005
Jarek Macedoński [23] Lake Garda, Italy OW CCR 316 m (1,040 ft)2018
Mark Ellyatt [36] Phuket Island, Thailand OW OC 313 m (1,030 ft)2003
Xavier Méniscus [37] Font Estramar, France C CCR 312 m (1,024 ft)2024
John Bennett [38] [nb 6] Puerto Galera, Philippines OW OC 308 m (1,010 ft)2001
Frédéric Swierczynski [39] Font Estramar, France C CCR 308 m (1,010 ft)2023
Krzysztof Starnawski [40] Lake Garda, Italy OW CCR 303 m (994 ft)2018
Will Goodman [22] Gili Trawangan, Indonesia OW CCR 290 m (951 ft)2014
Xavier Méniscus [41] Font Estramar, France C CCR 286 m (938 ft)2019
Nuno Gomes [28] [42] Boesmansgat, South Africa C OC 283 m (928 ft)1996
Krzysztof Starnawski [43] Dahab, Egypt OW CCR 283 m (928 ft)2011
Jim Bowden [44] Zacatón, Mexico C OC 282 m (925 ft)1994
Krzysztof Starnawski [45] [46] Lake Viroit, Albania C CCR 278 m (912 ft)2016
Han Ting GuangXi, China C CCR 277 m (909 ft)2023
Gilberto de Oliveira [28] [47] Lagoa Misteriosa, Brazil C OC 274 m (899 ft)2002
Nuno Gomes [28] Dahab, Egypt OW OC 271 m (889 ft)2004
David Shaw [28] [48] [nb 6] Boesmansgat, South Africa C DR 271 m (889 ft)2004
Frédéric Swierczynski Mescla, France C CCR 267 m (876 ft)2016
Pascal Bernabé [28] Corsica, France OW OC 266 m (873 ft)2005
Sheck Exley [28] [49] [nb 6] Nacimiento del Mante, Mexico C OC 265 m (869 ft)1989
Krzysztof Starnawski [50] [51] Hranice Abyss, Czechia C CCR 265 m (869 ft)2015
Sheck Exley [28] [44] [nb 6] Zacatón, MexicoC OC 264 m (866 ft)1989
Luca Pedrali [52] Lake Garda, Italy OW CCR 264 m (866 ft)2017
Sheck Exley [28] [44] [nb 6] Boesmansgat, South Africa C SCUBA 263 m (863 ft)1993
Xavier Méniscus [53] Font Estramar, France C CCR 262 m (860 ft)2015
Mark Ellyatt [ citation needed ] Phuket Island (?), Thailand OW OC 260 m (853 ft)2003
Qian Chen [54] Daxing Spring, ChinaC CCR 258 m (846 ft)2023
John Bennett [38] [nb 6] Puerto Galera, Philippines OW OC 254 m (833 ft)2000
Michele Geraci [55] Bordighera, Italy OW OC 253 m (830 ft)2014
Jordi Yherla [56] Font Estramar, France C CCR 253 m (830 ft)2014
Nuno Gomes [28] Boesmansgat, South AfricaC OC 252 m (827 ft)1994
Don Shirley [57] Boesmansgat, South Africa C CCR 250 m (820 ft)2005
Wacław Lejko [58] [59] [nb 6] Lake Garda, Italy OW OC 249 m (817 ft)2017
Xavier Méniscus [60] Font Estramar, France C CCR 248 m (814 ft)2013
Karen van den Oever [61] Boesmansgat, South Africa C OC 246 m (807 ft)2022
Xavier Méniscus Goul de la Tannerie, France C CCR 246 m (807 ft)2023
C.J. Brossett [62] Gulf of Mexico OW OC 245 m (804 ft)2019
Richard Harris, Craig Challen [63] Pearse Resurgence, New Zealand C CCR 245 m (804 ft)2020
Frédéric Swierczynski [64] [65] Red Lake, Croatia C CCR 245 m (804 ft)2017
Guy Garman [66] [nb 6] St. Croix, U.S. Virgin Islands OW OC 244 m (800 ft)2015
Dariusz Wilamowski [67] Lake Garda, Italy OW OC 243 m (797 ft)2012
Xavier Méniscus Goul de la Tannerie, France C CCR 243 m (797 ft)2019
Alexandre Fox Goul de la Tannerie, France C CCR 242 m (794 ft)2017
Jim Bowden [68] Zacatón, Mexico C OC 240 m (800 ft)1993
Xavier Méniscus Goul de la Tannerie, France C CCR 240 m (787 ft)2014
Pascal Bernabé [69] Fontaine de Vaucluse, France C OC 240 m (787 ft)1997

Air

A severe risk in ultra-deep air diving is deep water blackout, or depth blackout, a loss of consciousness at depths below 50 metres (160 ft) with no clear primary cause, associated with nitrogen narcosis, a neurological impairment with anaesthetic effects caused by high partial pressure of nitrogen dissolved in nerve tissue, and possibly acute oxygen toxicity. [70] The term is not in widespread use at present, as where the actual cause of blackout is known, a more specific term is preferred. The depth at which deep water blackout occurs is extremely variable and unpredictable. [71] Before the popular availability of trimix, attempts were made to set world record depths using air. The extreme risk of both narcosis and oxygen toxicity in the divers contributed to a high fatality rate in those attempting records. In his book, Deep Diving, Bret Gilliam chronicles the various fatal attempts to set records as well as the smaller number of successes. [72] From the comparatively few who survived extremely deep air dives:

Deep air dives
Depth [nb 7] YearNameLocationEComment
94 m (308 ft)1947 Frédéric Dumas [72] Mediterranean Sea OWA member of the GRS (Groupement de Recherches Sous-marines, Underwater Research Group headed by Jacques Cousteau).
100 m (330 ft)1957 Eduard Admetlla [73] Isla de Las Palomas OWHead of the Underwater Section of the «Submarine Research and Recovery Centre»
102 m (335 ft)1969Frank Salt [72] Chinhoyi Caves C
106  msw (345  fsw)1988Marty Dunwoody [72] Bimini OWWomen's deep dive record
107  msw (350  fsw)1961Hal Watts [72] FloridaOW
109  msw (355  fsw)1961Jean Clarke Samazen [72] FloridaOW
110  msw (360  fsw)1965 Tom Mount, Frank Martz [72] FloridaOW
120  msw (390  fsw)1965Hal Watts, A.J. Muns [72] FloridaOW
126 m (415 ft)1970Hal Watts [72] Mystery SinkC
131 m (430 ft)1959Ennio Falco, Alberto Novelli, Cesare Olgiai Gulf of Naples OWEmploying the Pirelli Explorer, "Maior" model, a two-stage regulator (patented by Novelli and Buggiani) equipped with a lung bag and soda lime filter for CO2 removal, in order to reuse the exhaled air. Only two of the three divers managed to reach the depth in a certified way: Novelli, the organizer of the event and inventor of the regulator, forgot to punch the plate for proving the descent. [74]
134  msw (437  fsw)1968Neal Watson, John Gruener [72] [75] Bimini OW
135  msw (440  fsw)1971Ann Gunderson [72] [nb 6] Bahamas OWWomen's deep dive record
139  msw (452  fsw)1990 Bret Gilliam [72] Roatán OWUnusually, Gilliam remained largely functional at depth and was able to complete basic maths problems and answer simple questions written on a slate by his crew beforehand.
142 m (466 ft)1971 Sheck Exley [76] [nb 6] Andros Island OWExley was only supposed to go down to 91 m (299 ft) in his capacity as a safety diver (although he had practised several dives to 120 m (390 ft) in preparation), but descended to search for the dive team after they failed to return on schedule. Exley almost made it to the divers, but was forced to turn back due to heavy narcosis and nearly blacking out.
146  msw (475  fsw)1993 Bret Gilliam [72] EL Salvador OWAgain, Gilliam reported no effects from narcosis or oxygen toxicity.
150  msw (490  fsw)1994Dan Manion [72] Nassau OW155  msw (506  fsw) claimed, but not officially recognised. [77] Manion reported he was almost completely incapacitated by narcosis and has no recollection of time at depth. [28]
156 m (512 ft)1999Mark Andrews [20] Puerto Galera, PhilippinesOWAt the maximum depth of 156.4 metres (513 ft) Andrews lost consciousness, his deep support diver John Bennett (on mixed gas), inflated his BC to initiate his ascent. While ascending he regained consciousness.

E Environment: OW = Open water, C = Cave

In deference to the high accident rate, the Guinness World Records have ceased to publish records for deep air dives, after Manion's dive. [28]

Fatalities during depth record attempts

See also

Related Research Articles

Nitrox refers to any gas mixture composed of nitrogen and oxygen that contains less than 78% nitrogen. In the usual application, underwater diving, nitrox is normally distinguished from air and handled differently. The most common use of nitrox mixtures containing oxygen in higher proportions than atmospheric air is in scuba diving, where the reduced partial pressure of nitrogen is advantageous in reducing nitrogen uptake in the body's tissues, thereby extending the practicable underwater dive time by reducing the decompression requirement, or reducing the risk of decompression sickness .The two most common recreational diving nitrox mixes are 32% and 36% oxygen, which have maximum operating depths of about 110 feet and 95 feet (29 meters respectively.

<span class="mw-page-title-main">Nitrogen narcosis</span> Reversible narcotic effects of respiratory nitrogen at elevated partial pressures

Narcosis while diving is a reversible alteration in consciousness that occurs while diving at depth. It is caused by the anesthetic effect of certain gases at high partial pressure. The Greek word νάρκωσις (narkōsis), "the act of making numb", is derived from νάρκη (narkē), "numbness, torpor", a term used by Homer and Hippocrates. Narcosis produces a state similar to drunkenness, or nitrous oxide inhalation. It can occur during shallow dives, but does not usually become noticeable at depths less than 30 metres (98 ft).

<span class="mw-page-title-main">Trimix (breathing gas)</span> Breathing gas consisting of oxygen, helium and nitrogen

Trimix is a breathing gas consisting of oxygen, helium and nitrogen and is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving.

Heliox is a breathing gas mixture of helium (He) and oxygen (O2). It is used as a medical treatment for patients with difficulty breathing because this mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a patient to breathe in and out of the lungs. It is also used as a breathing gas diluent for deep ambient pressure diving as it is not narcotic at high pressure, and for its low work of breathing.

<span class="mw-page-title-main">Technical diving</span> Extended scope recreational diving

Technical diving is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced via appropriate skills, knowledge, and experience. Risk can also be managed by using suitable equipment and procedures. The skills may be developed through specialized training and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.

<span class="mw-page-title-main">Diving medicine</span> Diagnosis, treatment and prevention of disorders caused by underwater diving

Diving medicine, also called undersea and hyperbaric medicine (UHB), is the diagnosis, treatment and prevention of conditions caused by humans entering the undersea environment. It includes the effects on the body of pressure on gases, the diagnosis and treatment of conditions caused by marine hazards and how relationships of a diver's fitness to dive affect a diver's safety. Diving medical practitioners are also expected to be competent in the examination of divers and potential divers to determine fitness to dive.

<span class="mw-page-title-main">Scuba diving</span> Swimming underwater, breathing gas carried by the diver

Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.

Hydreliox is an exotic breathing gas mixture of hydrogen, helium, and oxygen. For the Hydra VIII mission at 50 atmospheres of ambient pressure, the mixture used was 49% hydrogen, 50.2% helium, and 0.8% oxygen.

Argox is the informal name for a scuba diving breathing gas consisting of argon and oxygen. Occasionally the term argonox has been used to mean the same mix. The blend may consist of varying fractions of argon and oxygen, depending on its intended use. The mixture is made with the same gas blending techniques used to make nitrox, except that for argox, the argon is added to the initial pure oxygen partial-fill, instead of air.

Peter B. Bennett was the founder and a president and CEO of the Divers Alert Network (DAN), a non-profit organization devoted to assisting scuba divers in need. He was a professor of anesthesiology at Duke University Medical Center, and was the Senior Director of the Center for Hyperbaric Medicine and Environmental Physiology at Duke. Bennett is recognized as a leading authority on the effects of high pressure on human physiology.

<span class="mw-page-title-main">Latent hypoxia</span> Lung gas and blood oxygen concentration sufficient to support consciousness only at depth

Latent hypoxia is a condition where the oxygen content of the lungs and arterial blood is sufficient to maintain consciousness at a raised ambient pressure, but not when the pressure is reduced to normal atmospheric pressure. It usually occurs when a diver at depth has a lung gas and blood oxygen concentration that is sufficient to support consciousness at the pressure at that depth, but would be insufficient at surface pressure. This problem is associated with freediving blackout and the presence of hypoxic breathing gas mixtures in underwater breathing apparatus, particularly in diving rebreathers.

Hydrox, a gas mixture of hydrogen and oxygen, is occasionally used as an experimental breathing gas in very deep diving. It allows divers to descend several hundred metres. Hydrox has been used experimentally in surface supplied, saturation, and scuba diving, both on open circuit and with closed circuit rebreathers.

<span class="mw-page-title-main">Scuba gas planning</span> Estimation of breathing gas mixtures and quantities required for a planned dive profile

Scuba gas planning is the aspect of dive planning and of gas management which deals with the calculation or estimation of the amounts and mixtures of gases to be used for a planned dive. It may assume that the dive profile, including decompression, is known, but the process may be iterative, involving changes to the dive profile as a consequence of the gas requirement calculation, or changes to the gas mixtures chosen. Use of calculated reserves based on planned dive profile and estimated gas consumption rates rather than an arbitrary pressure is sometimes referred to as rock bottom gas management. The purpose of gas planning is to ensure that for all reasonably foreseeable contingencies, the divers of a team have sufficient breathing gas to safely return to a place where more breathing gas is available. In almost all cases this will be the surface.

<span class="mw-page-title-main">Scuba gas management</span> Logistical aspects of scuba breathing gas

Scuba gas management is the aspect of scuba diving which includes the gas planning, blending, filling, analysing, marking, storage, and transportation of gas cylinders for a dive, the monitoring and switching of breathing gases during a dive, efficient and correct use of the gas, and the provision of emergency gas to another member of the dive team. The primary aim is to ensure that everyone has enough to breathe of a gas suitable for the current depth at all times, and is aware of the gas mixture in use and its effect on decompression obligations, nitrogen narcosis, and oxygen toxicity risk. Some of these functions may be delegated to others, such as the filling of cylinders, or transportation to the dive site, but others are the direct responsibility of the diver using the gas.

Human physiology of underwater diving is the physiological influences of the underwater environment on the human diver, and adaptations to operating underwater, both during breath-hold dives and while breathing at ambient pressure from a suitable breathing gas supply. It, therefore, includes the range of physiological effects generally limited to human ambient pressure divers either freediving or using underwater breathing apparatus. Several factors influence the diver, including immersion, exposure to the water, the limitations of breath-hold endurance, variations in ambient pressure, the effects of breathing gases at raised ambient pressure, effects caused by the use of breathing apparatus, and sensory impairment. All of these may affect diver performance and safety.

<span class="mw-page-title-main">History of scuba diving</span>

The history of scuba diving is closely linked with the history of the equipment. By the turn of the twentieth century, two basic architectures for underwater breathing apparatus had been pioneered; open-circuit surface supplied equipment where the diver's exhaled gas is vented directly into the water, and closed-circuit breathing apparatus where the diver's carbon dioxide is filtered from the exhaled breathing gas, which is then recirculated, and more gas added to replenish the oxygen content. Closed circuit equipment was more easily adapted to scuba in the absence of reliable, portable, and economical high pressure gas storage vessels. By the mid-twentieth century, high pressure cylinders were available and two systems for scuba had emerged: open-circuit scuba where the diver's exhaled breath is vented directly into the water, and closed-circuit scuba where the carbon dioxide is removed from the diver's exhaled breath which has oxygen added and is recirculated. Oxygen rebreathers are severely depth limited due to oxygen toxicity risk, which increases with depth, and the available systems for mixed gas rebreathers were fairly bulky and designed for use with diving helmets. The first commercially practical scuba rebreather was designed and built by the diving engineer Henry Fleuss in 1878, while working for Siebe Gorman in London. His self contained breathing apparatus consisted of a rubber mask connected to a breathing bag, with an estimated 50–60% oxygen supplied from a copper tank and carbon dioxide scrubbed by passing it through a bundle of rope yarn soaked in a solution of caustic potash. During the 1930s and all through World War II, the British, Italians and Germans developed and extensively used oxygen rebreathers to equip the first frogmen. In the U.S. Major Christian J. Lambertsen invented a free-swimming oxygen rebreather. In 1952 he patented a modification of his apparatus, this time named SCUBA, an acronym for "self-contained underwater breathing apparatus," which became the generic English word for autonomous breathing equipment for diving, and later for the activity using the equipment. After World War II, military frogmen continued to use rebreathers since they do not make bubbles which would give away the presence of the divers. The high percentage of oxygen used by these early rebreather systems limited the depth at which they could be used due to the risk of convulsions caused by acute oxygen toxicity.

<span class="mw-page-title-main">Outline of underwater diving</span> List of articles related to underwater diving grouped by topical relevance

The following outline is provided as an overview of and topical guide to underwater diving:

References

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Footnotes

  1. All depths specified for sea water. Fractionally deeper depths may apply in relation to freshwater due to its lower density.
  2. Oxygen toxicity depends upon a combination of partial pressure and time of exposure, individual physiology, and other factors not fully understood. NOAA recommends that divers do not expose themselves to breathing oxygen at greater than 1.6 bar p O2, which occurs at 66 metres (217 ft) when breathing air.
  3. Assuming crystal clear water; surface light may disappear completely at much shallower depths in murky conditions. Minimal visibility is still possible far deeper. Deep sea explorer William Beebe reported seeing blueness, not blackness, at 1400 feet (424 metres). "I peered down and again I felt the old longing to go farther, although it looked like the black pit-mouth of hell itself—yet still showed blue." (William Beebe, "A Round Trip to Davey Jones's Locker", The National Geographic Magazine, June 1931, p. 660.)
  4. Statistics exclude military divers (classified), and commercial divers (commercial diving to those depths on scuba is not permitted by occupational health and safety legislation). In 1989, the US Navy Experimental Diving Unit published a paper that included a section on results from tests on the use of rebreathers at 850 ft (259 m).
  5. In 2007 a Turkish Navy [ clarification needed ] diver dived with a closed-circuit rebreather to a depth of 998 feet (304 m) off the coast of Cyprus, but that dive has not been independently verified. His dive was aborted due to equipment failure. It was a Turkish Navy experimental dive.[ citation needed ]
  6. 1 2 3 4 5 6 7 8 9 10 Subsequently died during diving accident.
  7. As given in the references. Metre sea water and feet sea water, as well as metre/feet fresh water are actually units of pressure. A conversion to the true depth would require information about the water's density (dependent on temperature and – if applicable salinity). Depth in metres and feet if measured by a shot line.

Further reading